There are many useful systems which contain and/or operate using a fluid (gas, liquid or combination of both). For example, automobiles have several systems which contain and utilize a fluid in their operation including the fuel system, the exhaust system, the heating, cooling and ventilation (HVAC) system, and the hydraulic power steering and brake systems, to name a few. Moreover, numerous industrial machines, household HVAC systems, and other devices utilize a fluid to operate. Such fluids include, for example, gases such as air or evaporated system liquid, fuel, hydraulic fluids, manufactured gases and liquids, and many other fluids.
In almost all circumstances, it is important, and in many cases crucial, that these fluid systems be properly sealed to prevent leakage of the system fluid. As an example, in an automobile fuel system, the gas tank and gas lines must be thoroughly sealed to prevent gasoline fumes from polluting the air and also to prevent leaking fuel from creating a fire hazard, not to mention the obvious benefit of conserving gasoline. In HVAC systems, it is important to seal the ducting which transports the conditioned air in order to maintain the efficiency of the systems. Air leaks tend to do nothing but heat or cool an attic, wall interior or other undesired space.
In many cases, leaks in fluid systems are very difficult to detect and/or locate because the leak is small or in a location not easily accessible. Accordingly, a variety of methods and devices have been devised to detect leaks in fluid systems. The most common leak detectors utilize a visual indicator to locate a leak so that the leak may be repaired. Some of the visual indicators include liquid dyes. The visual indicator is dispensed into the fluid system and leaks are detected by locating places on the system where the visual indicator has escaped the system. For instance, a liquid dye will leave a trace of dye at the leak and smoke will billow out through the leak. The liquid dyes are most useful for detecting leaks in fluid systems which utilize a liquid and are not so useful for gas systems or systems which must seal vapors created by the system fluid. Still, liquid leaks are typically easier to detect than gas and vapor leaks because the liquid itself is usually visible.
Vaporized dyes and smoke are most useful for detecting leaks in gas systems and systems which have vapors. In some cases, vaporized dye may be added to the smoke such that a trace of dye is left at the leak as the smoke flows through the leak. In general, devices for producing smoke for leak detection comprise a sealed chamber in which smoke is generated by vaporizing a smoke-producing fluid using a heating element. The smoke within the sealed chamber is forced out of the chamber through an outlet port by air pressure from a source of compressed air pumped into the sealed chamber. However, all of the previously disclosed smoke generating devices contact the smoke-producing fluid with the heating element to produce smoke by one of two methods. The first method is to locate the heating element within a reservoir of smoke-producing fluid. For example, U.S. Pat. No. 5,107,698, issued Apr. 28, 1992 to Gilliam, describes a smoke generating apparatus which has the heating element at least partially submerged within the smoke producing fluid in the fluid reservoir.
The drawbacks to a device in which the heating element is submerged within the smoke producing fluid are numerous. First of all, the level of the fluid within the chamber must be accurately controlled. This requires frequent monitoring and adjustment of the fluid level. Because the heating element is located within the fluid, the temperature of the heating element and the smoke chamber must also be accurately monitored and controlled in order to prevent combustion or explosion of the smoke-producing fluid. Worse yet, the fluid in the reservoir is heated and cooled with every use of the device, which tends to break down integrity of the fluid (such as oil). Also, in such recirculating designs, the fluid is easily contaminated by particulate and smoke by-products created by the smoke-producing process. The contaminants fall directly into the fluid reservoir because the smoke producing site is located directly within the fluid reservoir. The degraded fluid can cause several problems including ignition of the fluid, toxicity of the produced smoke and a decrease in smoke producing efficiency. This creates a serious maintenance issue requiring the regular replacement of the degraded fluid in the reservoir. Accordingly, the degrading of the fluid reduces reliability, may create a risk of combustion or explosion within the fluid reservoir, and the smoke produced with the contaminated fluid may have toxic components.
The second method of delivering the smoke-producing fluid to the heating element is to blow or spray the fluid onto the heating element. Examples of devices having this type of fluid delivery are described in U.S. Pat. No. 5,859,363, issued Jan. 12, 1999, to Gouge; U.S. Pat. No. 5,922,944, issued Jul. 13, 1999, to Pieroni et al.; U.S. Pat. No. 6,142,009, issued Nov. 7, 2000, issued to Loblick; U.S. Pat. No. 6,392,227, issued May 21, 2002, issued to Banyard et al.; U.S. Pat. No. 6,439,031, issued Aug. 27, 2002, to Pieroni et al.; and U.S. Pat. No. 6,526,808, issued Mar. 4, 2003, to Pieroni et al. In each of these devices, the smoke-producing fluid is blown, sprayed or atomized through a nozzle onto a heating element located above the fluid reservoir. Pressurized air is used to blow, spray or atomize the fluid through the nozzle. The heating element is purposely disposed above the fluid reservoir so that the blown, sprayed or atomized fluid which is not converted into smoke will return to the reservoir.
Again, this type of fluid delivery system has many drawbacks. For one, there must be a minimum amount of air pressure and air flow in order to spray the fluid onto the heating element. This prevents the device from being able to vary the flow rate of smoke being fed to the system being leak checked. A flow valve on the smoke outlet usually cannot be used to reduce the pressure and flow rate because the pressure drop through such valves causes at least some of the smoke to condense thereby reducing the amount of smoke produced. Also, the minimum amount of air pressure required by the smoke machine may exceed the pressure capacity of some systems which it is desired to leak check (for example, some automobile systems can only hold 4 inches of water pressure). Moreover, these smoke machines which require air flow to draw fluid into the air stream and/or spray the fluid toward the heating element are rendered inoperative if the flow rate is reduced below the operating level. This reduction may be caused by the system not having a large enough leak or by the use of a flow control value at either the inlet or outlet of the machine.
Furthermore, because the fluid is circulated back from the heating element to the fluid reservoir, this type of device suffers from the same contamination and degraded smoke producing fluid problems as described above.
Accordingly, there is a need for an improved method and device for producing smoke for detecting leaks in fluid systems which overcomes the deficiencies of previous devices. The device should be safe, reliable, compact, easy to use and maintain, and have a relatively low manufacturing and retail cost, compared to previously known machines.